Method and device for producing synthetic hydrocarbons

ABSTRACT

A method producing synthetic hydrocarbons includes producing synthesis gas. An initial step, carbon or a mixture of carbon and hydrogen is brought into contact with water at a temperature of 800-1700° C. The synthesis gas is converted into synthetic functionalised and/or non-functionalised hydrocarbons by means of a Fischer Tropsch process wherein it is brought into contact with a suitable catalyst, and wherein water in which a portion of the synthetic hydrocarbons is dissolved results as a by-product. At least a portion of the water that is produced as a by-product is supplied to the initial step. The hydrocarbons that are dissolved in the water decompose into particle-like carbon and hydrogen at the high temperature. The carbon is converted into CO in the presence of water and at a high temperature and forms a portion of the synthesis gas that is produced. In this way, a costly process for cleaning half of the water that is produced as a by-product is avoided.

RELATED APPLICATIONS

This application corresponds to PCT/EP2015/060699, filed May 13, 2015, which claims the benefit of German Application No. 10 2014 006 996.6, filed May 13, 2014, the subject matter of which is incorporated herein by reference in its entirely.

BACKGROUND OF THE INVENTION

The present invention relates to a method and an apparatus for producing synthetic hydrocarbons in which a smaller amount of waste water is produced.

From WO/2013/091879, there is known a method for the production of synthetic functionalised and/or non-functionalised hydrocarbons which comprises the decomposition of a hydrocarbon-containing fluid into an H₂/C-aerosol consisting of carbon C and hydrogen H₂ in a hydrocarbon converter, directing at least a part of the aerosol from the hydrocarbon converter into a C-converter as well as introducing H₂O from an external source into the C-converter. The H₂O is mixed with the H₂/C-aerosol in the C-converter whereby the H₂O and the carbon are converted at a high temperature into a gas mixture consisting of carbon monoxide CO and hydrogen. The carbon monoxide and the hydrogen are converted into synthetic hydrocarbons in a CO-converter by means of a catalyst in a Fischer Tropsch process. In addition to the synthetic hydrocarbons, approximately the same quantity of water, which is referred to as product water, is also produced as a by-product in the Fischer Tropsch process. A portion of the hydrocarbons produced in the Fischer Tropsch process is dissolved in the product water. The solubility of hydrocarbons in water amounts to approximately 400 ppm. If the product water is discharged untreated, the dissolved hydrocarbons can pollute the environment. Consequently, substantial capital outlays and operating costs are required for cleaning or for the treatment of the product water.

SUMMARY

The object of the present invention is to provide a method and an apparatus for the production of hydrocarbons wherein the outlay required for treating the product water can be reduced.

This object is achieved by a method for the production of synthetic hydrocarbons wherein synthesis gas is produced in that, in a step a), carbon is brought into contact with water or a mixture of carbon and hydrogen is brought into contact with water, namely, at a temperature of 800-1700° C. Thereafter, in a step b), the synthesis gas is converted into synthetic functionalised and/or non-functionalised hydrocarbons by means of a Fischer Tropsch process wherein it is brought into contact with a suitable catalyst and wherein water in which a portion of the synthetic hydrocarbons is dissolved results as a by-product. Then, in a step c), at least a portion of the water that was produced as a by-product is supplied to the step a). The hydrocarbons dissolved in the water decompose at the high temperature in the step a) into particle-like carbon and hydrogen. The carbon is converted into CO in the presence of water and at the high temperature in the step a) and forms part of the produced synthesis gas. In this way, a costly process of cleaning half of the water that was produced in the step b) as a by-product is avoided.

Advantageously, the temperature of the water produced as a by-product is controlled or regulated when being supplied to the step a) to at least a decomposing temperature at which the synthetic hydrocarbons dissolved therein are decomposed into carbon and hydrogen. Thus, in the presence of water vapour, the particle-like carbon resulting from the decomposing step is converted into gaseous CO which can easily be led away and subjected to further processing.

In this method, the carbon is preferably present in the form of C-particles which are mixed with hydrogen to form an aerosol. The H₂/C-mixture is thus present as a fluid which can be easily transported in a plant for carrying out the method. Moreover, a step of separating the carbon and hydrogen, which are both at a high temperature, can be omitted and the technical effort can be reduced. Furthermore, the hydrogen can serve as a source of energy.

Advantageously, before being brought into contact with water in step a), carbon is produced by decomposing a hydrocarbon-containing fluid by supplying energy to the exclusion of oxygen. In this way, fine carbon particles which also contain heat energy can be produced. The heat energy of the carbon provides at least a portion of the energy required for the conversion in the step a).

The decomposition of the hydrocarbon-containing fluid is preferably carried out in a hydrocarbon converter which is at least partly cooled by the water that is produced as a by-product. Too great a thermal loading of the hydrocarbon converter is thereby prevented and its life span is extended. This embodiment is particularly advantageous if temperatures of more than 1000° C. occur in the hydrocarbon converter.

In one advantageous embodiment, a portion of the water produced as a by-product (product water) is vaporised at a temperature above the decomposing temperature of the synthetic hydrocarbons dissolved in the water and the vapour is used for propelling a steam turbine. Consequently, a portion of the product water which cannot be used in step a) can serve for the production of energy. The synthetic hydrocarbons dissolved in the water decompose above the decomposing temperature into particle-like carbon and gaseous hydrogen. The carbon is in turn converted into gaseous CO in the presence of water. The water can easily be separated from the gaseous CO and from the gaseous hydrogen by a condensation process after passing through the steam turbine.

The object specified above is also achieved by an apparatus or a plant for the production of synthetic hydrocarbons which comprises a hydrocarbon converter that is adapted for decomposing a hydrocarbon-containing fluid into the form of a H₂/C-aerosol and which comprises at least one process chamber having at least one hydrocarbon inlet for a hydrocarbon-containing fluid and at least one C-outlet for C-particles or a H₂/C-aerosol and at least one unit for introducing energy into the process chamber, wherein the energy consists at least partly of heat. Furthermore, the apparatus comprises a C-converter for the step of converting carbon or hydrocarbon and water which comprises a process chamber having an inlet for at least water, an inlet for at least carbon and a synthesis gas outlet; wherein the C-outlet of the hydrocarbon converter is connected to the C-inlet for at least carbon of the C-converter. Furthermore, the apparatus comprises a CO-converter which is adapted for carrying out a Fischer Tropsch process for the production of synthetic functionalised and/or non-functionalised hydrocarbons and which comprises a process chamber in which a catalyst is arranged and which has means for guiding the synthesis gas into contact with the catalyst and a control unit for controlling or regulating the temperature of the catalyst and/or the synthesis gas to a predetermined temperature, wherein the process chamber of the CO-converter is connected to the synthesis gas outlet of the C-converter. The CO-converter comprises a water outlet for the water which is produced as a by-product during the production of synthetic hydrocarbons. The apparatus also comprises a water line which runs from the water outlet of the CO-converter to the inlet for at least water of the C-converter. At least a portion (preferably half) of the water that is produced as a by-product and in which synthetic hydrocarbons are also dissolved can be fed into the C-converter without the need for a costly cleaning process.

Another embodiment of the apparatus comprises heat exchanger means for cooling the hydrocarbon converter or a synthesis gas line between the C-converter and the CO-converter, wherein the water line runs from the water outlet of the CO-converter to the heat exchanger means and from the heat exchanger means to the inlet for at least water of the C-converter. In this embodiment, before being introduced into the C-converter, the product water additionally serves for cooling the hydrocarbon converter and thereby extends its life span.

Preferably, the hydrocarbon converter, its C-outlet, the C-converter and its C-inlet for at least carbon are constructed in such a way that carbon and hydrogen that are formed in the hydrocarbon converter are fed together into the C-converter. A simple construction for the apparatus is thereby achieved and hot hydrogen can be used as a source of energy for heating the C-converter.

In one embodiment of the apparatus, the hydrocarbon converter and the C-converter are combined into a combined converter. Hereby, the process chamber of the hydrocarbon converter is formed by a hydrocarbon converter zone and the process chamber of the C-converter is formed by a C-converter zone of the combined converter, and the C-outlet of the hydrocarbon converter and the inlet for at least carbon of the C-converter are formed by a transition between the hydrocarbon converter zone and the C-converter zone. Thus, heat loss between the hydrocarbon converter and the C-converter is prevented and a simple structure for the entire apparatus is achieved.

In an embodiment in which the apparatus is provided with heat exchanger means for cooling the hydrocarbon converter or with a synthesis gas line between the C-converter and the CO-converter, the apparatus further comprises a steam turbine having turbine blades and a steam inlet. The steam inlet of the steam turbine is connected to the heat exchanger means and is adapted for guiding a portion of the water, which is produced as a by-product and is being fed through the heat exchanger means, in the form of a vapour to the turbine blades. The portion of the product water that is not used in the C-converter can thus be used for the production of energy. Furthermore, the hydrocarbons dissolved in the product water can be converted into gaseous materials (CO and H₂) which can easily be separated from the water by condensing the vapour after the steam turbine.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail hereinafter with reference to particular embodiments with the aid of the drawings.

FIG. 1 is an illustration of an apparatus for the production of synthetic hydrocarbons; and

FIG. 2 is an illustration of an alternative apparatus for the production of synthetic hydrocarbons.

DESCRIPTION

It should be noted that in the following description, the expressions above, below, right and left as well as similar indications refer to the alignments or arrangements illustrated in the Figures and only serve for the description of the exemplary embodiments. These expressions are not however to be understood in a restrictive sense. Furthermore, the same reference signs are used to a certain extent in the different Figures insofar as they refer to the same or similar parts. In the present application furthermore, processes and devices are described which involve “hot” materials or which implement “hot” processes. In connection with this description, the expression “hot” is intended to describe a temperature of over 200° C. and preferably over 300° C. Insofar as synthetic hydrocarbons are mentioned in the present application, all synthetic functionalised and/or non-functionalised hydrocarbons are meant thereby.

FIG. 1 schematically illustrates an apparatus 1 for the production and manufacture of synthetic hydrocarbons. The apparatus 1 comprises a CO-converter 3 for the production of synthetic hydrocarbons, a C-converter 5 and a hydrocarbon converter 7. The basic operational sequence for the production and manufacture of synthetic hydrocarbons in accordance with this description is also clear from FIG. 1.

The CD-converter 3 is a Fischer Tropsch converter which catalytically converts a synthesis gas into synthetic functionalised and/or non-functionalised hydrocarbons and water (so-called product water in the form of a by-product). The CO-converter 3 comprises a process chamber in which a catalyst is arranged, further means for guiding synthesis gas into contact with the catalyst and a control unit for controlling or regulating the temperature of the catalyst and/or the synthesis gas to a pre-determined temperature. The synthesis gas is fed via a synthesis gas inlet 9 into the process chamber. The hydrocarbons are removed from the CO-converter 3 via a hydrocarbon outlet 11 and the product water is discharged from an H₂O outlet 13. Various versions of Fischer Tropsch reactors and Fischer Tropsch processes which need not be illustrated in detail here are known to the skilled person. The main reaction equations read as follows:

nCO+(2n+1)H₂→C_(n)H2_(n+2) +nH₂O for alkanes

nCO+(2n)H₂→C_(n)H_(2n) +nH₂O for alkenes

nCO+(2n)H₂→C_(n)H_(2n+1)OH+(n−1)H₂O for alcohols

The Fischer Tropsch processes can be carried out as a high-temperature process or as a low-temperature process wherein the process temperatures generally lie between 200 and 400° C. Known variants of the Fischer Tropsch process are, inter alia, the high load synthesis process, the Synthol synthesis process and the SMDS process of the company Shell (SMDS=Shell Middle Distillate Synthesis). Typically, a hydrocarbon compound consisting of liquid gases (propane, butane), gasoline, kerosene (diesel oil), soft paraffin, hard paraffin, methane, diesel fuel or a mixture of several of these is produced by a Fischer Tropsch converter. The Fischer-Tropsch-Synthese process is exothermic as is known to the skilled person. The heat of reaction from the Fischer Tropsch process can, for example, be used by means of a heat exchanger (which is not shown in the Figures) for preheating water or a hydrocarbon-containing fluid.

The synthesis gas for the Fischer Tropsch process comes from the C-converter 5 which may be any suitable C-converter that can produce a synthesis gas (Syngas) from carbon (C) and water (H₂O). The C-converter 5 comprises a process chamber having an inlet 15 for at least water, a C-inlet 17 for at least carbon and a synthesis gas outlet 19. The synthesis gas outlet 19 of the C-converter 5 is connected to the synthesis gas inlet 9 of the CO-converter 3.

In the C-converter 5, H₂O is fed over hot carbon or else it is introduced in the form of water vapour in a stream of carbon and hydrogen and mixed therewith in order to be converted in accordance with the chemical equation C+H₂O→CO+H₂. The following reactions occur in the C-converter 5:

C+H₂O→CO+H₂+131.38 kJ/mol endothermic

CO+H₂O→CO₂+H₂−41.19 kJ/mol exothermic

The following reaction takes place at the Boudouard equilibrium:

2C+O₂→2CO+172.58 kJ/mol endothermic

Since all three reactions are in equilibrium with one another, the process in the C-converter 5 preferably takes place at high temperatures of from 800 to 1700° C., preferably 1000 to 1600° C., because the second reaction would be preferred at a lower temperature. The heat necessary for reaching this temperature is made available primarily by the material which is emerging from the hydrocarbon converter 7, as will be described in more detail hereinbelow. The water (H₂O) in the C-converter 5 is vaporous under these conditions and can thus be directly introduced in the form of steam. When the apparatus 1 is in operation, the addition of water is controlled in such a way as to avoid having a surplus of water in order to prevent a steep cooling process. In the event of excessive cooling in the C-converter 5, the second reaction would likewise preferentially occur.

The C-converter 5 works best at high temperatures of from 1000 to 1600° C. in order to repress the exothermic Water-Shift reaction CO+H₂O→CO₂+H₂ and so optimize the proportion of carbon monoxide in the synthesis gas. The reactions in the C-converter 5 are known to the skilled person and will not therefore be described in more detail here.

The hydrocarbon converter 7 comprises a hydrocarbon inlet 21, a C-outlet 23 as well as an optional hydrogen outlet 25. The hydrocarbon converter 7 and the C-converter 5 are arranged in such a manner that the C-outlet 23 of the hydrocarbon converter 7 is connected by a direct connection 27 to the C-inlet 17 of the C-converter 5 wherein the C-outlet 23 can also directly form the C-inlet 17 of the C-converter 5. Carbon can thus be transported directly from the hydrocarbon converter 7 into the C-converter 5.

The hydrocarbon converter 7 is any form of hydrocarbon converter which can convert or decompose the incoming hydrocarbons into carbon and hydrogen. The hydrocarbon converter 7 can be operated thermally or can be operated by means of a plasma. In a thermally operated hydrocarbon converter, a hydrocarbon fluid being introduced into a reaction chamber is heated by any type of heat source up to a decomposing temperature. In a hydrocarbon converter operating with plasma, the input of energy is effected by means of a plasma arc. A hydrocarbon fluid that is being fed-in decomposes at the decomposing temperature into carbon and hydrogen. If possible, the process of decomposing the hydrocarbons should take place in absence of oxygen in order to prevent the unwanted formation of carbon oxides or water. However, small quantities of oxygen which are introduced with the hydrocarbons for example are not detrimental to the process.

The hydrocarbon converter 7 comprises a process chamber having an inlet for a hydrocarbon-containing fluid, at least one unit for introducing decomposing energy into the fluid and at least the above-mentioned C-outlet 23. The decomposing energy is made available at least partially by the heat which is produced e.g. by a plasma (plasma reactor). However, it could be made available in some other manner (thermal reactor). The decomposing step is effected primarily by heat. The fluid should be heated to over 1000° C. and in particular to a temperature above 1500° C. In the case of a plasma-operated hydrocarbon converter, any suitable gas which is supplied from the exterior or which is produced in the hydrocarbon converter can be selected as the plasma gas. For example, inert gases, e.g. argon or nitrogen, are suitable as the plasma gas. On the other hand, hydrogen gas H₂, CO or synthesis gas are suitable candidates since hydrogen gas is produced in any case during the process of decomposing the hydrocarbons and CO or synthesis gas is produced during the further reaction of the carbon.

In the illustrated embodiment, a Kvaerner reactor is employed as the hydrocarbon converter 7 which makes the requisite heat available by means of a plasma arc in a plasma burner 29. However, other reactors are known which work at lower temperatures and in particular below 1000° C. and which, apart from the heat, introduce additional energy into the hydrocarbon such as by means of a microwave plasma for example. As will be described in more detail hereinafter, the invention takes into consideration both of these reactor types (and also those which work without a plasma) and in particular too, those which work in combination with one another. Hydrocarbon converters which work at a temperature in the process chamber of more than 1000° C. are called high-temperature reactors, while those which work at temperatures below 1000° C., especially a temperature between 200° C. and 1000° C., are called low-temperature reactors.

Hydrogen and carbon are generated from hydrocarbons (C_(n)H_(m)) in the hydrocarbon converter 7 by means of heat and/or a plasma. The hydrocarbons are preferably introduced into the process chamber in gaseous form. In the case of hydrocarbons that are in liquid form under standard conditions, they can be changed info gaseous form before being introduced into the hydrocarbon converter 1, or they could also be fed-in in finely atomised form. All these forms are called fluids here. The hydrocarbon-containing fluid preferably consists of a stream of natural gas, methane, liquid gases or heavy oil and in particular, preferably of a stream of conventional or non-conventional natural gas as well as liquid gases (“wet gases”).

Furthermore, the apparatus 1 comprises a product water line 31 which runs from the H₂O-outlet 13 of the CO-converter 3 to the inlet for at least water of the C-converter. The product water line 31 runs first to a heat exchanger 33 which is attached to the hydrocarbon converter 7 for cooling purposes and then on further to the inlet 15 for at least water of the C-converter 5. Alternatively, a product water line 31′ can extend from the H₂O-outlet 13 of the CO-converter 3 directly to the inlet 15 of the C-converter 5 as shown in the Figures by dashed lines.

The heat exchanger 33 can, for example, be attached to the outer wall of the hydrocarbon converter 7 or may be integrated therein. The heat exchanger 33 may comprise one or more pipes or chambers. For example, the product water line 31 may run at least in parts of the outer wall of the hydrocarbon converter 7. The product water line 31 can be directed around the outer wall of the hydrocarbon converter 7 several times for example. Furthermore, the heat exchanger 33 can be in the form of a double-walled casing of the hydrocarbon converter 7. Furthermore, the function of the heat exchanger 33 can be provided by gaps between the outer walls of a plurality of adjacently located hydrocarbon converters 7 and C-converters 5. In this case, the adjacently located hydrocarbon converters 7 and C-converter 5 can be enclosed by a common outer casing so that gaps are formed between the converters 5, 7 themselves and between the converters 5, 7 and the outer casing. The product water can be fed through these gaps and thereby heated.

In one embodiment which is not shown in the Figures, the heat exchanger 33 or an additional heat exchanger is attached to a synthesis gas line between the C-converter 5 and the CO-converter 3. In operation, a heat exchanger 33 attached thereto cools the synthesis gas which is being fed from the C-converter 5 (more than 850° C.) to the CO-converter 3 (approx. 250-400° C.). The further explanations in regard to the heat exchanger 33 also apply to this embodiment which is not shown in the Figures.

Furthermore, the apparatus 1 comprises an optional mixer 35 which is adapted for mixing additional hydrogen with the synthesis gas from the C-converter. The additional hydrogen can be supplied over a line 36 from any source of hydrogen 37, wherein the source of hydrogen 37 is a hydrogen storage vessel or a hydrocarbon converter 7 for example. In a (not shown) embodiment which does not comprise a mixer 35, additional hydrogen can be fed directly into the CO-converter 3.

After the C-outlet 23 of the hydrocarbon converter 7 (e.g. at the inlet of the following C-converter 5), there may be arranged an optional filter 39 which is adapted for filtering out carbon-containing particles from a C/H₂ aerosol at the temperatures prevailing here. The optional filter 39 could also form an integral component of the C-converter 5. Such a filter which could also be integrated in the C-converter 5 is known from the German patent application No. 10 2013 013 443 for example. When a filter 39 is employed, substantially only carbon in the form of C-particles enters into the C-inlet 17 of the C-converter 5 when the apparatus is in operation. In the following, it is assumed that a filter 39 is not provided so that a C/H₂ aerosol is thus fed into the first C-converter 5. However, the exemplary embodiments function in exactly the same way if only C-particles which were separated from the hydrogen by the filter 39 are passed on.

Due to the high temperature in the hydrocarbon converter 7, the heat exchanger 33 also becomes very hot, i.e. is heated to several hundred degrees Celsius by the waste heat that is developed when the apparatus is in operation. Consequently, the product water being introduced into the heat exchanger 33 will be present in the form of a vapour and will be under pressure. The vapour contains mainly water and small proportions of carbon monoxide and hydrogen. Carbon monoxide and hydrogen develop from the hydrocarbons dissolved in the product water as soon as the decomposing temperatures of the dissolved hydrocarbons are reached. Furthermore, the apparatus 1 comprises a steam pipe 41 which is connected to the heat exchanger 33. A portion of the pressurised vapour can be extracted from the heat exchanger 33 and be fed to a steam turbine 43 via the steam pipe 41. The steam turbine 43 comprises a turbine exhaust gas line 45 which leads to a separating device 47. The constituents of the vapour are separated from one another in the separating device. An example of a separating device comprises a condenser in which the vaporous water condenses into liquid water. The condensed water does not contain any dissolved hydrocarbons and can be removed through a water line 48. The carbon monoxide and the hydrogen are gaseous at both high and at low temperatures and do not condense during the cooling process in the condenser. Consequently, carbon monoxide and hydrogen in the form of a gas mixture (synthesis gas) are removed from the separating device through a gas line 49. Carbon monoxide and hydrogen can then be reintroduced into the apparatus 1 at a suitable location, for example, into the C-converter 5, into the mixer 35 or into the CO-converter 3.

Insofar as the product of the CO-converter 3 is a mixture of hydrocarbons which, after the isolation and refinement thereof, cannot be further processed directly or sold profitably as a finished product, these hydrocarbons (for example, methane or short-chain paraffins) can be fed back into the process that is described here. For this purpose, the apparatus 1 comprises an optional return pipe 50 with the assistance of which a portion of the synthetically produced hydrocarbons can be fed back to the hydrocarbon inlet 21 of the hydrocarbon converter 7. Depending upon the composition of the returned, synthetically produced hydrocarbons, further treatment and/or separation thereof from non-suitable hydrocarbons is effected before they are introduced into the hydrocarbon inlet 21.

The operation of the apparatus 1 in accordance with FIG. 1 will now be described in more detail. It is assumed in the following that the hydrocarbon converter 7 is a high-temperature reactor of the Kvaerner type. Hydrocarbon-containing fluids (especially in gaseous form) are introduced into the hydrocarbon converter 7 via the hydrocarbon inlet 11. If the hydrocarbon is methane (CH₄) for example, then 1 mol carbon and 2 mol hydrogen are obtained from 1 mol methane. In the case of other hydrocarbons, correspondingly different molar ratios of carbon and hydrogen result. The hydrocarbons are converted in the hydrocarbon converter 7 at about 1600° C. in accordance with the following reaction equation, wherein the supplied energy is heat which is produced in the plasma by means of electrical energy:

C_(n)H_(m)+energy→nC+m/2H₂

With a properly controlled processing operation, the hydrocarbon converter 7 (Kvaerner reactor) is capable of attaining an almost complete conversion of the hydrocarbon into its constituents hydrogen and carbon when in continuous operation (in dependence on the temperature, there is a more than 94% conversion of the hydrocarbons, see above). After the decomposing step, the hydrogen and the carbon are present in the form of a mixture, i.e. a H₂/C-aerosol.

The H₂/C-aerosol is extracted from the hydrocarbon converter 7 and fed into the C-converter 5. The hydrogen 5 serves as a carrier gas for the carbon (C-particles) and does not impair the conversion step in the C-converter, the hydrogen however can serve as an additional heat carrier medium. The H₂/C-aerosol is fed cut from the C-outlet 23 into the C-inlet 17 of the C-converter 5. Thus, in operation, not only carbon but also hydrogen come out of the C-outlet 23. In like manner, not only carbon but also hydrogen flow into the inlet 17. Since the H₂/C-aerosol emerging from the hydrocarbon converter 7 is at a high temperature (preferably over 1000° C.), the heat energy contained therein can be used for maintaining the temperature required for the conversion step in the C-converter 5 which preferably works at a temperature of approx. 1000° C.

The hot vapour (water vapour as well as hydrogen and carbon monoxide) is introduced from the product water line 31 via the inlet 15 for at least water into the C-converter 5. Water vapour is thereby mixed with the H₂/C-aerosol and thus brought into contact with the hot carbon.

The C-converter 5 works best at high temperatures (preferably at a temperature >800° C. and particularly preferred at >1000° C.) since this is an endothermic reaction and the Water-Shift reaction which competes therewith is an exothermic reaction. The reaction, which is known to the skilled person, is dependent on pressure and temperature and will not be described in detail here. Either the quantity of water introduced into the C-converter 5 or the quantity of carbon can be controlled and/or regulated by suitable means.

C+H₂O→CO+H₂ ΔH=+131.38 kJ/mol

Nevertheless, the Boudouard equilibrium is also the limiting factor here, which is why there is almost exclusively a mixture of carbon monoxide and hydrogen at temperatures above 1000° C. and in the absence of a surplus of water. The vapour being introduced is already preheated to a high temperature of approx. 700-900° C. since the product water has already been fed through the heat exchanger 33 used for cooling the hydrocarbon converter 7. The largest portion of the hydrocarbons dissolved in the product water has already been decomposed into carbon and hydrogen in the heat exchanger 33 by the waste heat of the hydrocarbon converter 7. The hydrocarbons present in the product water are not heatproof but are decomposed pyrolytically. The waste heat from the hydrocarbon converter 7 is sufficient for attaining the cracking or decomposing temperature of the hydrocarbons. Since the hydrocarbons in the product water are highly diluted (about 400 ppm), there will be no aggregation of carbon and thus too no occurrence of large C-particles under these conditions, something which could lead to a blockage in the lines. Rathermore, the carbon continues to react to synthesis gas when in stade nascendum. Any remaining hydrocarbons which are possibly still being carried in the vaporous product water are decomposed into carbon and hydrogen at the high temperature in the following C-converter 5.

In the case of the optional embodiment wherein the product water is fed through the product water line 315 and thus not through the heat exchanger 33, the product water is at a lower temperature which corresponds approximately to the temperature after the emergence from the CO-converter 3 (200-350° C.).

The gas mixture consisting of CO and H₂ from the C-converter 5 is then fed to the CO-converter 3 and converted by the Fischer Tropsch process mentioned above into synthetic hydrocarbons and product water. The product water is then fed back into the C-converter 5 through the product water line 31 in the manner mentioned above.

In operation, about half of the product water produced in the CO-converter 3 can be reintroduced into the C-converter. In comparison with the state of the art, this thus results in the advantage that only half as much of the product water has to be cleaned before it can be discharged into the environment.

A further improvement can be achieved if more product water than is required in the C-converter 5 is fed through the heat exchanger 33 and evaporated. Due to the high temperatures in the heat exchanger, the hydrocarbons dissolved in the product water decompose (decomposing temperature >450° C.) into carbon and hydrogen directly in the heat exchanger 33. The heat exchanger therefore functions like an (above mentioned) thermal hydrocarbon converter. The carbon similarly reacts in the heat exchanger 33 with the likewise existing water vapour in accordance with the equation specified above C+H₂O→CO+H₂ and the already mentioned vapour mixture made up of water vapour, carbon monoxide and hydrogen thereby develops. The surplus proportion of the vapour mixture that is not introduced into the C-converter 5 can be fed via the steam pipe 41 to the steam turbine 43. The steam turbine 43 can be used for producing energy for operating an electrical generator for example.

After the vapour mixture has performed its work in the steam turbine 43, it is fed via the turbine exhaust gas line 45 to the separating device 47. In the separating device 47, the water vapour is condensed to form liquid water; and the hydrogen and the carbon monoxide are stored or supplied to the process at a suitable location, as described above. The condensed water is no longer contaminated and can be discharged into the environment.

The construction of the apparatus 1 shown in FIG. 2 substantially corresponds to the construction shown in FIG. 1. Consequently, the same reference signs are used for designating similar or equivalent elements. The description of the equivalent elements is omitted here. In the apparatus 1 of FIG. 2 and in contrast to the apparatus depicted in FIG. 1, the hydrocarbon converter 7 and the C-converter 5 are integrated to form a combined converter 7/5 and have a common process chamber which comprises two zones, namely, a hydrocarbon converter zone 7 and a C-converter zone 5. The transition between the two zones 7 and 5 is illustrated in FIG. 2 by a dashed transition line 23/17. A plasma burner 29 is arranged above the transition line 23/17 in the zone 7 and, in operation, the step of decomposing the hydrocarbons that are being introduced into C-particles and hydrogen takes place therein. In operation, the step of introducing the vaporous product water (as mentioned above, the vapour contains mainly water and very small proportions of carbon monoxide and hydrogen) is effected in the zone 5 below the transition line 23/17. In principle, the transition line 23/17 at the point of transition between the two zones 7, 5 corresponds to the C-outlet 23 and the C-inlet 17 of the embodiment in accordance with FIG. 1. The remaining construction of the apparatus in FIG. 2 corresponds to the embodiment in accordance with FIG. 1, and therefore will not be described again in detail here.

The operation of the apparatus in FIG. 2 is similar to that described above for FIG. 1. Hydrocarbon-containing fluids (especially in gaseous form) are introduced into the hydrocarbon converter zone 7 via the hydrocarbon inlet 11. If the hydrocarbon is methane (CH₄) for example, then 1 mol carbon and 2 mol hydrogen are produced from 1 mol methane. In the case of other hydrocarbons, correspondingly different molar ratios of carbon and hydrogen result. The hydrocarbons are converted in the hydrocarbon converter zone 7 at about 1600° C. in accordance with the following reaction equation, wherein the supplied energy is heat which is produced in the plasma by means of electrical energy:

C_(n)H_(m)+energy→nC+m/2H₂

The hydrogen and carbon are present after the decomposition step as a mixture, i.e. in the form of an H₂/C-aerosol.

The H₂/C-aerosol is fed from the hydrocarbon converter zone 7 toward the transition line 23/17 and is fed into the C-converter zone 5. Thus, in operation, not only carbon but also hydrogen are fed above the transition line 23/17. The hydrogen serves as a carrier gas for the carbon (C-particles) and does not impair the conversion step in the C-converter zone 5. Since the H₂/C-aerosol emerging from the hydrocarbon converter zone 7 is at a high temperature (preferably over 1000° C.), the heat energy contained therein can be used for maintaining the temperature required for the conversion step in the C-converter zone 5 in which a temperature of approx. 1000° C. preferably prevails.

The hot vapour (water vapour, hydrogen and carbon monoxide) is introduced into the C-converter zone 5 from the product water line 31 via the inlet 15 for at least water. Water vapour is thus mixed with the H₂/C-aerosol and thereby brought into contact with the hot carbon. A high temperature is maintained in the C-converter zone 5 (>800° C. and particularly preferred at >1000° C.) since this is an endothermic reaction and the Water-Shift reaction which competes therewith is an exothermic reaction. Either the quantity of water that is introduced into the C-converter 5 or the quantity of carbon can be controlled and/or regulated by suitable means.

C+H₂O→CO+H₂ ΔH=+131.38 kJ/mol

Nevertheless, also here the Boudouard equilibrium is the limiting factor, which is why there is almost exclusively a mixture of carbon monoxide and hydrogen at temperatures above 1000° C. and in the absence of a surplus of water. The vapour being introduced is already preheated to a high temperature of approx. 700-900° C. since the product water has already been fed through the heat exchanger 33 for the purposes of cooling the hydrocarbon converter zone 7 of the combined converter 7/5. A portion of the hydrocarbons dissolved in the product water has already been decomposed into carbon and hydrogen in the heat exchanger 33 by the waste heat of the hydrocarbon converter zone 7. Hydrocarbons which are possibly still being conveyed in the vaporous product water are decomposed into carbon and hydrogen due to the high temperature in the C-converter zone 5.

In the case of the optional embodiment wherein the product water is fed through the product water line 31′ and thus not through the heat exchanger 33, the product water is at a lower temperature which corresponds approximately to the operating temperature of the CO-converter 3 (250-350° C.).

The gas mixture consisting of CO and H₂ from the C-converter zone 5 is then fed to the CO-converter 3 and is converted by the Fischer Tropsch process mentioned above into synthetic hydrocarbons and product water. The product water is then fed back into the C-converter zone 5 through the product water line 31 in the manner mentioned above.

In operation, also in the case of the apparatus according to FIG. 2, about half of the product water produced in the CO-converter 3 can be reintroduced into the C-converter zone 5. In comparison with the state of the art, this thus results in the advantage that only half as much of the product water has to be cleaned before it can be discharged into the environment. As described above with reference to FIG. 1, a further improvement can also be achieved in the embodiment of FIG. 2 if more product water than is required in the C-converter zone 5 is fed through the heat exchanger 33 and evaporated. Due to the high temperatures in the heat exchanger, the hydrocarbons dissolved in the product water have already decomposed (decomposing temperature>450° C.) into carbon and hydrogen in the heat exchanger 33. The heat exchanger thus functions like a thermal hydrocarbon converter. The carbon similarly reacts in the heat exchanger 33 with the likewise existing water vapour in accordance with the equation specified above C+H₂O→CO+H₂, and a vapour mixture consisting of water vapour, carbon monoxide and hydrogen thereby is produced. The surplus proportion of the vapour mixture that is not introduced into the C-converter 5 can be fed via the steam pipe 41 to the steam turbine 43. After the vapour mixture has performed its work in the steam turbine 43. It is fed to the separating device 47 via the turbine exhaust gas line 45. In the separating device 47, the water vapour is condensed to form liquid water and the hydrogen and the carbon monoxide are stored or supplied to the process at a suitable location, as described above. The condensed water is no longer contaminated and can be discharged into the environment.

In all of the embodiments, the heat contained in the C-particles is sufficient to bring the water up to the temperature that is wanted in the C-converter or in the C-converter zone. Only for the case where the heat produced in the hydrocarbon converter 3 is not sufficient to achieve the desired conversion temperature of approximately 1000° C., an optional additional heating unit can be provided for heating up the C-converter or the C-converter zone 9. Such an additional heating unit could also be employed as a preheating unit in the region of a supply line for the water or carbon. The process of heating all the parts purely by means of the heat produced in the hydrocarbon converter 7 could last for too long a time in the beginning. The additional heating unit could therefore be employed just for the starting phase of the apparatus in order to bring the converters or medium-conveying parts of the apparatus up to an initial temperature so that the system will more rapidly achieve a desired temperature state.

Finally, the following example for the conversion process in the individual converters may be mentioned:

a) clear numbers:

Introduction into the hydrocarbon converter 7: 1043023 t methane

Introduction into the C-converter 6: 758115 t water

Output from the CO-converter: 1180527 t hydrocarbons (product)

By-product from the CO-converter: 1516231 t water

Consumed CO₂ 925999 t

b) standardized to 1000 t methane as starting material:

Introduction into the hydrocarbon converter 7: 1000 t methane

Introduction into the C-converter 5: 727 t water

Output from the CO-converter: 1132 t hydrocarbons (product)

By-product from the CO-converter: 1454 t water

Consumed CO₂ 888 t

In principle, one could also use the method in a conventional GtL plant (GtL=Gas to Liquid) which comprises a steam-reformer and a Fischer Tropsch converter and with which the synthesis gas is derived from methane or some other hydrocarbon by means of a steam reforming process. The basic equation thereby is usually:

CH₄+3H₂O═CO+3H₂+2H₂O

For technical reasons, about three mol water is utilised in the steam reforming process in accordance with the state of the art, of which two mol water then remain after the reformation step (but have been heated up therewith). In a conventional GtL plant using a steam-reformer, one could feed back the entire amount of process water of the CO-converter 3 that is produced as a by-product into the steam-reformer by applying the principles disclosed in this description. The rest of the water remaining after the pyrolysis of the hydrocarbons is then precipitated before the CO-converter 3.

The invention has been described on the basis of preferred embodiments, wherein the individual features of the embodiments described can be freely combined and/or exchanged with one another insofar as they are compatible. Likewise, individual features of the embodiments described can be omitted insofar as they are not compellingly necessary. For the skilled person, numerous modifications and arrangements are possible and obvious without thereby departing from the concept of the invention. 

1-11. (canceled)
 12. A method for producing synthetic hydrocarbons which comprises the following steps: a) producing synthesis gas by bringing carbon or a mixture of carbon and hydrogen into contact with water at a temperature of 800-1700° C.; b) converting the synthesis gas into synthetic functionalised and/or non-functionalised hydrocarbons by means of a Fischer Tropsch process by bringing the synthesis gas into contact with a suitable catalyst, wherein water results as a by-product in which a portion of the synthetic hydrocarbons is dissolved; and c) supplying at least a portion of the water that was produced as a by-product to the step a); wherein a portion of the water that is produced as a by-product is vaporised at a temperature above the decomposing temperature of the synthetic hydrocarbons dissolved in the water; and wherein the vapour is used for propelling a steam turbine (43).
 13. The method according to claim 12, wherein the temperature of the water, when being supplied to the step a), is controlled or regulated to at least a decomposing temperature at which the synthetic hydrocarbons dissolved therein are decomposed into carbon and hydrogen.
 14. The method according to claim 12, wherein the carbon is present as C-particles which are mixed with hydrogen to form an aerosol.
 15. The method according to claim 12, wherein the carbon, before the step of bringing it into contact with water in the step a), is produced by decomposing a hydrocarbon-containing fluid by supplying energy in the absence of oxygen.
 16. The method according to claim 15, wherein the step of decomposing the hydrocarbon-containing fluid is carried out in a hydrocarbon converter (7) which is at least partly cooled by the water that was produced as a by-product.
 17. An apparatus (1) for producing synthetic hydrocarbons which comprises the following: a hydrocarbon converter (7) for decomposing a hydrocarbon-containing fluid to form an H₂/C-aerosol which comprises at least one process chamber having at least one hydrocarbon inlet (21) for a hydrocarbon-containing fluid end at least one C-outlet (23) for C-particles or a H₂/C-aerosol and at least one unit (29) for introducing energy into the process chamber wherein the energy consists at least partly of heat; a C-converter (5) for converting carbon or hydrocarbon and water into a synthesis gas which comprises a process chamber having an inlet (15) for at least water; a C-inlet (17) for at least carbon and a synthesis gas outlet (19); wherein the C-outlet (23) of the hydrocarbon converter (7) is connected to the C-inlet (17) for at least carbon of the C-converter (5); a CO-converter (3) which is adapted for carrying out a Fischer Tropsch process for the production of synthetic functionalised and/or non-functionalised hydrocarbons and which comprises a process chamber in which a catalyst is arranged and having means for guiding the synthesis gas info contact with the catalyst and having a control unit for controlling or regulating the temperature of the catalyst and/or the synthesis gas to a pre-determined temperature, wherein the process chamber of the CO-converter (3) is connected to the synthesis gas outlet (19) of the C-converter (5); wherein the CO-converter (3) comprises a water outlet (13) for water which is produced as a by-product during the process of producing synthetic hydrocarbons; and a wafer line (31, 31′) which runs from the water outlet (13) of the CO-converter (3) to the inlet (15) for at least water of the C-converter (5); and a steam turbine (43) having turbine blades and a steam inlet; wherein the steam inlet of the steam turbine (43) is connected to the heat exchanger means (33) and is adapted for guiding a portion of the wafer which is produced as a by-product and is fed through the heat exchanger means (33) to the turbine blades in the form of a vapour.
 18. The apparatus (1) according to claim 17, which further comprises heat exchanger means (33) for cooling the hydrocarbon converter (7) or a synthesis gas line between the C-converter (5) and the CO-converter (3), and wherein a water line (31) runs from the wafer outlet (13) of the CO-converter (3) to tie heat exchanger means (33) and from the heat exchanger means (33) to the inlet (15) for at least water of the C-converter (5).
 19. The apparatus (1) according to claim 17, wherein the hydrocarbon converter (7), the C-outlet (23) thereof the C-converter (5) and the C-inlet (17) thereof for at least carbon are constructed in such a way that carbon and hydrogen which are formed in the hydrocarbon converter (7) are fed together into the C-converter (5).
 20. The apparatus (1) according to claim 17, wherein the hydrocarbon converter (7) and the C-converter (5) are combined into a combined converter 7/5; wherein the process chamber of the hydrocarbon converter (7) and the process chamber of the C-converter (5) are formed by a hydrocarbon converter zone and a C-converter zone of the combined converter; and wherein the C-outlet (23) of the hydrocarbon converter (7) and the C-inlet (17) for at least carbon of the C-converter (5) are formed by a transition between the hydrocarbon converter zone and the C-converter zone. 